1. Field of the Invention
This invention relates to a focus detecting device.
2. Description of the Prior Art
The focus detecting device disclosed, for example, in Japanese Laid-open Patent Application No. 39543/1975 (Japanese Patent Application No. 68068/1974) corresponding to U.S. application Ser. No. 377,809 (filed on July 9, 1973) is one in which the optical images of an object are formed on a pair of photoelectric element arrays and the differences between the photoelectric outputs of photoelectric elements located at corresponding positions on the two photoelectric element arrays are taken out, whereafter a correlated output is obtained as the sum of the absolute values of the differences and the focused condition of an objective lens is detected from the minimum value of the correlated output. According to this method, however, the correlated output is not standardized and therefore, it assumes various waveforms depending on the brightness distribution of the object to be focused, as indicated by solid line and broken line in FIG. 4 of the accompanying drawings. Accordingly, in order to detect the focused condition, it is necessary to move the objective lens at least once from the shortest distance to infinity.